For example, in various rotary machines including a rotor such as a compressor, a turbine, a pump, an engine, and so on, a bearing device is used to rotatably support the rotor.
As the bearing device, a gas bearing device including a tilting pad is known. This tilting pad serves to swingably support a bearing pad having a pad surface slidably in contact with the rotor. In the gas bearing device, as the rotor rotates, a gas which is present around the rotor is drawn into a space between an outer circumferential surface of the rotor and an inner circumferential surface of the bearing pad to form a membrane (gas membrane) formed of the gas, and thus the rotor is rotatably supported. Here, the gas is drawn into the space between the outer circumferential surface of the rotor and the inner circumferential surface of the bearing pad and then compressed, and a dynamic pressure is generated. Due to this dynamic pressure, the rotor is supported without coming into direct contact with the bearing pad.
For example, Patent Documents 1 and 2 disclose such a bearing device having a constitution in which a ceramic coating and a fixed lubricant coating are respectively applied to an inner circumferential surface of a bearing pad to minimize frictional resistance generated between the bearing pad and a rotor when a dynamic pressure due to a gas membrane is small.